IgE-mediated allergic asthma, rhinitis, food allergy, atopic dermatitis, anaphylaxis cost annual 18 billions in medical costs and loss of productivity in this country. Regulation of IgE production by B cells is orchestrated by Th2 cytokines. This paradigm dictates a treatment modality of IgE-mediated hypersensitive diseases that diminishes endogenous levels of IL-4, thereby IgE production by IgE-committed B cells. Alternatively, studies initiated by PI indicated that following IgE immunization, CD8 T cells play an important role in inhibiting IgE production by IgE-committed B cells, and profound IgE deficiency ensued and is maintained in IgE-immunized mice. This observation leads to the current passive anti-IgE therapeutic product concept. However, this treatment modality suffers drawbacks in failing to inhibit IgE synthesis as well as to remove circulating IgE-anti-IgE complexes, which accumulates to levels 10 fold higher, compared to the levels prior to treatment. And it is yet to be determined whether patients may be given a second heavy dose without eliciting neutralizing antibodies, including internal image-type of antibodies that potentially can cause mast cell degranulation. It is imperative to design alternative therapeutic modality based on active IgE immunization with higher safety standards. Herein, we provide a long-term strategy of reducing IgE levels by active immunization with IgE cytotoxic peptides (ECP) that are independent of requirement of conformation. Since B cells and plasma cells of the IgE lineage exhibiting natural ECP onto the binding site pocket of MHC class I, these targets are Iysed by ECP-specific CTL due to active vaccination. The advantages of this commercial vaccine are: (i) ECP is sequence-dependent, and does not elicit anti-IgE; (ii) ECP is economic and its effect long-lasting. To achieve this immediate goal, our two Aims are: Aim I: To Determine the Structure of Natural Human IgE (huIgE) CTL Epitopes Restricted To HLA-A2.1 and Ascertain Their Efficacies with huIgE-Producing Cells. Aim II: To Determine Whether ECP-specific CTL Elicited By Active Immunization Inhibit Human IgE Production In A Pre-clinical Model of huIgE/HLA-A2.1 Transgenic Mice. PROPOSED COMMERCIAL APPLICATION: IgE cytotoxic peptide (ECP) vaccine aims at an open market of active allergy immunization. Unlike the conventional allergen-desensitization, ECP technology based on targeting the universal IgE epitope can desensitize allergic syndromes caused by a myriad of allergens with a booser dose. Furthernore, unlike the current passive anti-IgE therapy, ECP is economic for one or two injections; risk-free since it is directed to linear sequence not recognize by anti-IgE, as compared to the current anti-IgE therapy that may actually cause mast cell degranulation due to induction of anti-idiotype.